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Effects Of Drought Conditions On Microbial Communities In Native Rangelands, Abbie L. Lasater, Tiffany Carter, Charles Rice 2017 University of Arkansas, Fayetteville

Effects Of Drought Conditions On Microbial Communities In Native Rangelands, Abbie L. Lasater, Tiffany Carter, Charles Rice

Chemical Engineering Undergraduate Honors Theses

Climate change is a result of greenhouse gases released into the atmosphere. These changes are expected to cause extreme weather conditions, including severe storms. Large amounts of rain will fall in shorter periods of time, leading to heavy runoff, and increasing the severity of drought conditions within the soil (Zeglin et al. 2013).

Native grasslands occupy almost a quarter of the earth’s land surface and are valuable ecological resources. They contain soils with high concentrations of organic matter and play a key role in mitigating greenhouse gas emissions through carbon sequestration. There are a variety of grassland management techniques ...


A Study Of The Secondary Effects Of Hill Fertilization, Horace J. Harper 2017 Iowa State College

A Study Of The Secondary Effects Of Hill Fertilization, Horace J. Harper

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

A field, laboratory, and greenhouse study of secondary effects of hill fertilization was made using several different soils as follows: Carrington loam, Webster silt loam, Grundy silt loam, Knox silt loam, Marion silt loam, and Buckner coarse sand. The effect of hill fertilization on the root development of the corn plant was also investigated.

Acid phosphate was found to have a more pronounced effect on the hydrogen ion concentration of the soil solution than either ammonium sulfate or potassium chloride. In most cases the first effect of acid phosphate was to increase the acidity of the soil solution. In poorly ...


What Is Meant By Crop Availability Of Manure Nutrients?, John Sawyer, Antonio P. Mallarino 2017 Iowa State University

What Is Meant By Crop Availability Of Manure Nutrients?, John Sawyer, Antonio P. Mallarino

John E. Sawyer

Nutrient management guidelines in Iowa and other states use the words “manure nutrient availability” when suggesting manure application rates to supply nutrients needed by crops. People are sometimes confused about the meaning of the word “availability.” In fact, manure management guidelines across the region vary in the exact use and this contributes to confusion. Interestingly, Webster’s Ninth New Collegiate Dictionary includes “plant” and “nitrogen” in the definition of “available.” One definition is “present or ready for immediate use”, and another definition is “present in such chemical or physical form as to be usable (as by a plant) <~ nitrogen> …” So, why ...


Sensing Nitrogen Stress In Corn, John Sawyer, John Lundvall, Jennifer Hawkins, Dan Barker 2017 Iowa State University

Sensing Nitrogen Stress In Corn, John Sawyer, John Lundvall, Jennifer Hawkins, Dan Barker

John E. Sawyer

Determining the proper nitrogen (N) fertilization rate is important for the economic viability of corn production. A desire for high yields, fueled by low fertilizer N costs, led producers to apply rates that ensured adequate N rather than risk costly yield losses due to a shortage of N. Due to water quality concerns and recently high N fertilizer prices, management strategies are needed that can improve the efficiency and profitability of N use. With N application rates based on economic return instead of maximizing productivity, producers want to confirm that rate decisions are working adequately. Also, if unexpected N losses ...


Manure Resources, Jeffery Lorimor, Antonio Mallarino, John Sawyer, John Creswell 2017 Iowa State University

Manure Resources, Jeffery Lorimor, Antonio Mallarino, John Sawyer, John Creswell

John E. Sawyer

Using manure as a resource.


Nitrogen Application, John Sawyer, John Creswall 2017 Iowa State University

Nitrogen Application, John Sawyer, John Creswall

John E. Sawyer

Nitrogen (N) management planning for corn production.


Nutrient Management Plan, Antonio Mallarino, John Sawyer, Barbara Stewart, John Creswell 2017 Iowa State University

Nutrient Management Plan, Antonio Mallarino, John Sawyer, Barbara Stewart, John Creswell

John E. Sawyer

Management tools to help you develop a nutrient management plan and use the Iowa Phosphorus Index.


Crop Rotation, Jerald DeWitt, Michael Duffy, Gerald Miller, John Sawyer, John Creswell 2017 Iowa State University

Crop Rotation, Jerald Dewitt, Michael Duffy, Gerald Miller, John Sawyer, John Creswell

John E. Sawyer

Understanding the potential benefits of a crop rotation system.


Soil Testing, Antonio Mallarino, John Sawyer, John Creswell 2017 Iowa State University

Soil Testing, Antonio Mallarino, John Sawyer, John Creswell

John E. Sawyer

Establishing and using a soil testing program to more efficiently manage crop essential nutrients.


Phosphorus Application, Antonio Mallarino, John Sawyer, John Creswell 2017 Iowa State University

Phosphorus Application, Antonio Mallarino, John Sawyer, John Creswell

John E. Sawyer

Management tools that help in creating a phosphorus management plan.


Relationships Between Hydrogen Ion, Hydroxyl Ion And Salt Concentrations And The Growth Of Seven Soil Molds, Harlan W. Johnson 2017 Iowa State College

Relationships Between Hydrogen Ion, Hydroxyl Ion And Salt Concentrations And The Growth Of Seven Soil Molds, Harlan W. Johnson

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Comparatively few data have been recorded relative to the effect of hydrogen ion concentration on the development and activities of molds and other fungi, altho such records have been secured for the bacteria. For both groups much more work has been accomplished on the effect of titratable acidity. The importance of molds in transforming plant food in the soil has made advisable the securing of such data. The present paper records the results of a study of the limiting and optimum hydrogen and hydroxyl ion concentrations and the limiting concentrations of several salts as related to the growth of seven ...


The Color Of Soils In Relation To Organic Matter Content, P. E. Brown, A. M. O'Neal 2017 Iowa State College

The Color Of Soils In Relation To Organic Matter Content, P. E. Brown, A. M. O'Neal

Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

The color of soils has long been considered to indicate to some extent, at least, their fertility. For centuries farmers in the humid regions have been accustomed to select their land very largely on the basis of color. Dark colored soils have been preferred because experience has shown that such soils are usually more productive than light colored types. But just what the relation is between the color of soils and their fertility or crop-producing power has never been determined. It has been assumed that the organic matter or humus content, which is mainly responsible for the color of soils ...


Precision Drought Stress In Orchards: Rootstock Evaluation, Trunk Hydration And Canopy Temperature, Lance V. Scott 2017 Utah State University

Precision Drought Stress In Orchards: Rootstock Evaluation, Trunk Hydration And Canopy Temperature, Lance V. Scott

All Graduate Theses and Dissertations

In many areas, over half of all diverted water is used for irrigation. Tree fruit crops use a lot of water, but water productivity can be increased using properly-timed precision water stress. In addition to water conservation, increases in water productivity arise from better fruit quality, increased storage life and reductions in pruning and maintenance. One major hurdle to applying precision water stress in orchards is the lack of a reliable, automated method of determining tree water status. However, the influence of physiological characteristics such as rootstock vigor on water productivity are also important. Selecting the most appropriate rootstocks and ...


Detecting, Cloning, And Screening For Suppressors Of Rna Silencing In Maize Chlorotic Mottle Virus And Sugarcane Mosaic Virus, Nicole E. Bacheller 2017 University of Nebraska-Lincoln

Detecting, Cloning, And Screening For Suppressors Of Rna Silencing In Maize Chlorotic Mottle Virus And Sugarcane Mosaic Virus, Nicole E. Bacheller

Theses, Dissertations, and Student Research in Agronomy and Horticulture

Maize lethal necrosis disease (MLND) is one of the most important viral diseases of maize. MLND occurs when Maize chlorotic mottle virus (MCMV) co-infects the same plant with one of several potyviruses, including Sugarcane mosaic virus, Wheat streak mosaic virus or Maize dwarf mosaic virus. Originally prevalent in the Midwest and Peru in the 1970s, the disease was called corn lethal necrosis (CLN) and was controlled through breeding and sanitation. Recently, the disease has re-emerged in East Africa and is rapidly spreading and threatening the food sources of subsistence-farming populations. This re-emergence has raised several questions about the unknown molecular ...


How To Interpret Your Manure Analysis, Angela Rieck-Hinz, Thomas G. Miller, John E. Sawyer 2017 Iowa State University

How To Interpret Your Manure Analysis, Angela Rieck-Hinz, Thomas G. Miller, John E. Sawyer

John E. Sawyer

Manure analysis is a critical component of proper nutrient management planning. Table or book values of manure nutrient concentrations can serve as a starting point for planning purposes, but actual manure sample analysis provides a better indication of manure nutrient concentrations and will help better define application rates. Utilizing manure testing will help achieve the potential as a crop nutrient source, and result in reduced chance for misapplication that could lead to lower crop productivity or increased environmental risk.


Winter Rye Cover Crop Biomass Production, Degradation, And Nitrogen Recycling, Jose L. Pantoja, Krishna P. Woli, John E. Sawyer, Daniel W. Barker 2017 Universidad de las Fuerzas Armadas

Winter Rye Cover Crop Biomass Production, Degradation, And Nitrogen Recycling, Jose L. Pantoja, Krishna P. Woli, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Winter rye (Secale cereale L.) cover crop (RCC) use in corn (Zea mays L.) and soybean [Glycine max. (L.) Merr.] production can alter N dynamics compared to no RCC. The objectives of this study were to evaluate RCC biomass production (BP) and subsequent RCC degradation (BD) and N recycling in a no-till corn–soybean (CS) rotation. Aboveground RCC was sampled at spring termination for biomass dry matter (DM), C, and N. To evaluate BD and remaining C and N, RCC biomass was put into nylon mesh bags, placed on the soil surface, and collected multiple times over 105 d. Treatments ...


Maximum Soil Organic Carbon Storage In Midwest U.S. Cropping Systems When Crops Are Optimally Nitrogen-Fertilized, Hanna J. Poffenbarger, Daniel W. Barker, Matthew J. Helmers, Fernando E. Miguez, Daniel C. Olk, John E. Sawyer, Johan Six, Michael J. Castellano 2017 Iowa State University

Maximum Soil Organic Carbon Storage In Midwest U.S. Cropping Systems When Crops Are Optimally Nitrogen-Fertilized, Hanna J. Poffenbarger, Daniel W. Barker, Matthew J. Helmers, Fernando E. Miguez, Daniel C. Olk, John E. Sawyer, Johan Six, Michael J. Castellano

John E. Sawyer

Nitrogen fertilization is critical to optimize short-term crop yield, but its long-term effect on soil organic C (SOC) is uncertain. Here, we clarify the impact of N fertilization on SOC in typical maize-based (Zea mays L.) Midwest U.S. cropping systems by accounting for site-to-site variability in maize yield response to N fertilization. Within continuous maize and maize-soybean [Glycine max (L.) Merr.] systems at four Iowa locations, we evaluated changes in surface SOC over 14 to 16 years across a range of N fertilizer rates empirically determined to be insufficient, optimum, or excessive for maximum maize yield. Soil organic C ...


Nutrient Deficiencies And Application Injuries In Field Crops, John E. Sawyer 2017 Iowa State University

Nutrient Deficiencies And Application Injuries In Field Crops, John E. Sawyer

John E. Sawyer

No abstract provided.


Take A Good Soil Sample To Help Make Good Decisions, John Sawyer, Antonio Mallarino, Randy Killorn 2017 Iowa State University

Take A Good Soil Sample To Help Make Good Decisions, John Sawyer, Antonio Mallarino, Randy Killorn

John E. Sawyer

One of the most important steps in soil testing is collecting the soil sample. The soil sample is the fi rst part of the soil testing process and the foundation for information derived from laboratory analyses, soil test interpretations, and recommendations. Also, soil sampling is the largest source of errors in the soil testing process.

Remember why you are taking soil samples -- to obtain information on which you can base recommendations and decisions concerning fertilizer, manure, and limestone use.

A comprehensive soil fertility and organic matter map for each fi eld is desirable as a basis on which to adjust ...


Concepts And Rationale For Regional Nitrogen Rate Guidelines For Corn, John Sawyer, Emerson Nafziger, Gyles Randall, Larry Bundy, George Rehm, Brad Joern 2017 Iowa State University

Concepts And Rationale For Regional Nitrogen Rate Guidelines For Corn, John Sawyer, Emerson Nafziger, Gyles Randall, Larry Bundy, George Rehm, Brad Joern

John E. Sawyer

Nitrogen (N) is typically one of the largest corn fertilization expenses. Nitrogen application is critical because it significantly improves corn yield in many crop rotations. When choosing N rates, producers need to carefully consider both achieving most profitable economic return and advancing environmental stewardship.

In 2004, university agronomists from the Corn Belt states began discussions regarding N rate use for corn production. The reasons for the discussions centered on apparent differences in methods for determining N rates across states, misperceptions regarding N rate guidelines, and concerns about application rates as corn yields have climbed to historic levels. An outcome of ...


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